Health Library

What Are RASopathies?

RASopathies are a group of genetic conditions. They’re called RASopathies (raz-OP-uh-thees) because they’re caused by problems in the RAS pathway, which is one way cells in the body communicate.

The individual RASopathies are rare, but as a group:

• They’re among the most common genetic conditions. 
• They cause most genetic-related learning and development problems.

What Are the Signs & Symptoms of RASopathies?

RASopathies are a type of syndrome (SIN-drome). Syndromes are diseases, conditions, or disorders that involve a particular group of signs and symptoms.

All RASopathies can affect a child’s:

• heart
• brain
• eyes
• skin
• bones and muscles

Signs and symptoms of a RASopathy include:

• unusual facial features
• developmental delays
• growth delays
• heart problems
• bone problems
• gastrointestinal (feeding) problems

RASopathies also can increase a child’s risk for cancer.

What Are the Kinds of RASopathies?

RASopathies include:

• cardiofaciocutaneous syndrome
• Costello syndrome
• Legius syndrome
• neurofibromatosis type 1
• Noonan syndrome, including:
  • Noonan syndrome with multiple lentigines (brown spots on skin), formerly called LEOPARD syndrome
  • Noonan syndrome with loose anagen hair (hair in its active growth phase)

What Causes RASopathies?

The body’s protein cells communicate with each other in many ways. Good communication ensures the cells work as they should. When groups of proteins communicate with each other, they create a pathway. The signals the cells send along the pathway can cause them to:

• copy themselves to make more cells
• die off when the body doesn’t need more cells
• work in a different way

Changes in the genes (our genetic “blueprints”) in the RAS pathway cause the RASopathies. These happen when there’s a problem in one of the steps in the pathway. Cells react in ways they shouldn’t — for instance, multiplying when they should die off.

Sometimes, a RASopathy runs in families. A parent who has one has a 50% chance of passing it to a child. Other times, the change is “spontaneous.” This means that a child has the condition but the parents do not. This is called a new mutation.

What Else Should I Know?

The problems caused by RASopathies vary. Even children with the same condition can have differences in the problems it causes and how severe the problems are.

Children with RASopathies are cared for by a health care team that includes specialists in:

• genetics
• neurology
• cardiology
• endocrinology
• oncology
• ophthalmology
• developmental medicine

RASopathies are lifelong conditions. But medical care can help with many of the symptoms and problems they cause.